In the Internet Protocol (IP) era, it is often using the TDM transmission technology as the IP bottom layer bearer. TDM transmission technologies include E1, T1, and J1.
E1 is taken for example. Generally, E1 works in channelized mode. That is, each E1 frame is consisted of 32 timeslots. Except timeslot 0 which is used for synchronization and maintenance, all or certain of timeslot 1 to timeslot 31 may be used to bear IP data. When E1 is working in the channelized mode, IP data is borne on the channelized E1 (IPover channelized E1 for short). The corresponding protocol stack is IP/Peer-Peer Protocol (PPP)/High level Data Link Control (HDLC)/channelized E1. That is, IP packets are borne by PPP frames. PPP frames are borne by HDLC frames, and are mapped to specified timeslots of E1 frames. At this time, the timeslots used for transmitting HDLC frames must be specified in the devices at both ends that use E1 communication, thereby HDLC frames are normally sent and received, negotiation of PPP frames is accomplished, and IP packets are normally transmitted.
In the prior art, timeslots for E1 frames used by the HDLC frames may be pre-configured in the devices at both ends. However, the pre-configuration solution requires much human participation and results in heavy workload and poor efficiency.